The present invention relates to a cylinder lock and a key for the cylinder lock.
In the prior art, a key with an inner groove may be used for a cylinder lock. Such a key includes an elongated key plate. A key groove, or inner groove, extends in the longitudinal direction of the key plate and is formed between serrated walls in at least one surface of the key plate. Such a key is referred to as an inner groove key (refer to, for example, Japanese Laid-Open Patent Publication No. 7-259400). The inner groove key is difficult to duplicate. Further, a cylinder lock using the inner groove key is resistant to picking. For such reasons, grooved keys are used in various fields.
In recent years, a so-called electronic key system has been proposed to provide a higher level of security and improve convenience (refer to, for example, Japanese Laid-Open Patent Publication No. 2005-226254). In an electronic key system, identification codes are transmitted between a portable device and a locking device to lock and unlock the locking device. The identification codes are authenticated to ensure a high level of security. With the electronic key system, a key does not have to be inserted into a keyway. Due to its convenience, the use of electronic key systems in vehicles and houses has increased dramatically.
In this manner the electronic key system provides both security and convenience at high levels. Nevertheless, it is still desirable for a mechanical key to be on hand just in case the electronic key system fails to function normally for one reason or another (e.g., failure in the electric system or communication system). Accordingly, most portable devices are equipped with an emergency mechanical key. During an emergency, the emergency key is removed from the portable device and used to lock and unlock the locking device.
Based on thickness, portable devices for electronic key systems, which remotely controls locking and unlocking, may be classified into two types, a card-type and a box-type. An emergency key for a card-type portable device must be thin so that it can be accommodated in the portable device. However, it is preferable that the emergency key be thick due to the torque applied when turning the key in the cylinder lock to perform locking or unlocking. Thus, an emergency key for a box-type portable device is thick.
In the prior art, a thick key cannot be inserted into a cylinder lock designed for thin keys. Further, when inserting a thin key into a cylinder lock designed for thick keys, the thin key would be loose in the cylinder lock. This would hinder stable locking and unlocking with the thin key.
Selection of the type of portable device depends on the application or assumed user of the portable device. However, it is desirable that a cylinder lock, or key locking device, be applicable to both thin keys and thick keys. Accordingly, there is a strong demand for the development of such a key locking device.